Carbon nanotubes (CNT's) each have good thermal diffusion property and good conductivity. In view of the foregoing, an investigation has been conducted on a composite material using any one of the carbon nanotubes as a material for a thermal contact surface in a microprocessor.
An investigation has been conducted on a composite material containing a polymer material and a plurality of carbon nanotubes as a composite material useful as the material for a thermal contact surface in a microprocessor. The composite material is such that the plurality of carbon nanotubes are engaged in the polymer material in a vertical direction. High thermal diffusion property and high conductivity can be expressed as a result of such engagement of the plurality of carbon nanotubes in the polymer material in the vertical direction as described above (see Patent Literature 1).
The above-mentioned composite material utilizes the following characteristics (see the paragraph 0029 of Patent Literature 1). A carbon nanotube has good conductivity, and the carbon nanotube has a thermal conductivity in its lengthwise direction larger than a thermal conductivity in a direction vertical to the lengthwise direction.
Although the thermal diffusion property and the conductivity that can be expressed by the composite material described in Patent Literature 1 are at somewhat high levels, the composite material has been unable to express sufficiently high thermal diffusion property and sufficiently high conductivity when the composite material is assumed to be actually used as a material for a thermal contact surface in a microprocessor.
In addition, when the above-mentioned composite material is used as a material for a thermal contact surface in a microprocessor, the composite material is requested to be placed between the surfaces of two devices (such as a heat spreader and a heat sink) and surely fixed. Accordingly, the composite material is requested to be sufficiently bonded to the surface of each device. Further, in the above-mentioned production process for the microprocessor, the following need may arise. The two devices placed through the composite material is requested to be peeled and attached again for the purpose of, for example, the correction of a placement shift. Accordingly, the composite material is requested to be excellent in reworking property from the surface of each device (in other words, it is requested that the composite material can be easily peeled and bonded again without any adhesive residue).
As described above, no such composite material useful as a material for a thermal contact surface in a microprocessor as described below has been obtained yet. The composite material can express extremely high thermal diffusion property and extremely high conductivity, can express a sufficient adhesive strength in its surface, and is excellent in reworking property at the time of a bonding operation.    Patent Literature 1: JP 2007-284679 A